Robert Sciarrino/The Star-LedgerHigh-tech license plate readers are aiding police departments across the state. Pictured is a one-of-a-kind specialty license plate made by Inmates at Bayside State Prison in South Jersey.

PERTH AMBOY — The officer was in his car, driving in the downtown part of the city on July 26. He was visually scanning the streets, looking for any sign of trouble and in all directions, just as police officers always do.

But he had some high-tech help. As a car passed the patrol car going the opposite direction at Market and Second streets, an electronic pinging rang out, and a large picture of the license plate popped up on the screen in front of him.

The Automatic License Plate Reader, or ALPR, had taken a digital picture of the passing license plate — as it had done for every other car that passed by — and scanned it against national and local databases, finally determining it was stolen, all within seconds.

“It scans all the cars,” said Capt. Luis Guzman Jr. of the Perth Amboy police. “If the owner’s wanted for parking tickets, it will come up.”

The automated license plate reader, or ALPR, is becoming one of the fastest-growing tools in police work, experts say. The technology takes pictures of every license plate that passes by, then scans it against national and local databases – for stolen cars such as the one in Perth Amboy, Amber alerts, suspended licenses, even down to expired registrations. The state Attorney General’s Office put together a set of guidelines that went into effect in January 2011, when more and more departments started to use the systems. But even as the technology proliferates, the national American Civil Liberties Union is trying to figure out how many are out there in a nearly nationwide information request, including New Jersey.

“It is critical for the public to know whether adequate safeguards are in place to limit the collection and storage of each individual’s license plate information,” said Thomas MacLeod, the Open Government Project Fellow for the ACLU’s New Jersey chapter.

The ACLU is seeking records from 21 police departments in New Jersey, including most of the state’s biggest cities, as well as the New Jersey State Police. But the Garden State is not alone — the ACLU offices in 38 states also filed similar requests last week. The ACLU is looking to determine how many of the readers are in use, and how they’re being used by police.

“We have a lot of information we hope to get from these requests,” MacLeod said.

New Jersey has some rules in place for the burgeoning technology. The state Attorney General’s Office put out a directive in January 2011, which covers the usage of the machines. The technology is relatively new, according to the state Attorney General’s Office. The ALPR automatically and continually scans, focuses and photographs all license plates within range, then converts them into electronic text documents, which are then run through the “be on the lookout,” or “BOLO,” list – which can include information from the National Crime Information Center, the U.S. Department of Homeland Security, as well as the state Motor Vehicle Commission. They can be in moving police cars, such as is Perth Amboy, or at stationary locations, the Attorney General said.

Police have been permitted to manually “run the plates” since a 1998 state Supreme Court ruling in State v. Donis, the attorney general wrote. But those manual searches are much slower than the automatic program, which can scan and check on hundreds of plates per minute, experts say. So the directive written 18 months ago was an attempt to settle some of the potential “legal and policy issues” with the lightning-quick automatic readers. For instance, the Attorney General said an officer would have to take responsible action to make sure that the age and gender of a person in the car matches the description of the wanted person before actually stopping a car whose license number has a warrant out.

But the Attorney General also said that local authorities are also authorized to use an entire list of license plate numbers, not just ones that pop up as “wanted” plates, from the automatic readers to establish a list of cars near a crime scene – which might lead to discovery of evidence or information relevant to the crime, the state wrote in its directive.

The Perth Amboy officer, after noticing the alert, turned around and pursued the stolen car. Though the car got away at first, he and another officer found it hours later in the same neighborhood, with the driver still behind the wheel. They also noticed the ignition had been tampered with, the police allege. The Perth Amboy department has one reader on a single patrol car, and the Middlesex County prosecutor helped with the funding to pay for it, Guzman said.

A group of 25 readers were paid for with Homeland Security grants to protect critical infrastructure, said Gerry McAleer, the deputy chief of investigators at the Middlesex County Prosecutor’s Office. He did not want to identify where the ALPRs were in usage. But while some other parts of the country use the readers to pick up scofflaws for parking tickets and other fines, he said their use in Middlesex County is generally to catch criminals.

“Their use is pretty widespread now,” McAleer said. “It’s most useful for us to find cars used in crimes, like robberies or kidnappings.”

MacLeod said the ACLU is only attempting to look into the automatic readers to see how far their reach is. They haven’t yet taken a stance on how or when they’re used. But there are concerns with the potential of the technology, he said.

“The legitimate needs of public safety and law enforcement do not include tracking the movements of law-abiding citizens who take to the roads of New Jersey,” MacLeod said.

The technology has gotten good enough that the ALPRs can basically pick up every plate that comes within range — and even small police departments are now starting to use them, according to Dennis Jay Kenney, a professor in the department of criminal justice at the John Jay College of Criminal Justice.

Their upside is huge — when it comes to finding stolen cars, responding to cars wanted during Amber alerts, and other real-time responses to crime. But the possible abuse of private information about travel and peoples’ locations also exists, Kenney said.

“Put these together with EZ-Pass and cameras at intersections, and you could have a Big Brother scenario,” the professor said.